338 T. H. Morgan 
involves the whole problem of the nature of the chromosomes them- 
selves—a question about which we know at present almost noth- 
ing. If the size differences of the chromosomes means that they 
are qualitatively different, then the probable answer is that the 
quantitative difference depends on more of a particular kind of 
chromatin. But if the size differences of the chromosomes has 
only a genetic meaning and they are qualitatively identical or 
very similar, the probable answer is that the result 1s merely more 
chromatin. 
The case of Acholla multispinosa described by Payne, in which 
the single Y-element is quantitatively greater than the five chro- 
mosomes that form the X group (the mates of Y), may seem to be 
demonstrative in favor of the view that the result is not quanti- 
tative but qualitative. But even here we do not know whether 
five separate chromosomes might not be more active than the same 
material contained in one chromosome. ‘Tempting as it is to 
assume that the quantitative effects are due to the number of the 
sex chromosomes qualitatively different from the others, the evi- 
dence is still too imperfect to decide so important a question. We 
can safely leave the solution to the future, nevertheless this case of 
Acholla is extremely important. ‘The single large chromosome 
is confined to the male line. It seems arbitrary to ignore its 
function as a male-producing factor in development. ‘The evi- 
dence in favor of this view is at least as great as that for the acces- 
sory chromosome in other insects, and the main argument for 
ignoring it is that it does not fit in well with theories based on 
the accessories alone. 
In a recent analysis of the problem Castle proposes a view that 
has certain points of resemblance to a quantitative hypothesis, 
and at the same time attempts to make sex inheritance a phase of 
Mendelism. “The female is the male condition plus a distinct 
unit character Mendelian in heredity.”’ In support of this view 
Castle points out how the case of Abraxas can be accounted for on 
the basis of the special assumptions made by Bateson and Punnett. 
The essence of Castle’s position is that maleness and femaleness are 
not allelomorphic, but there exists a unit character whose presence 
produces a female, its absence a male. A further analysis of the 
